Quick Recap Monitoring and Controlling

Difference and connection In put Transformation processes Out put Feedforward control Feedback control Concurrent control

Scope Control Scope control involves controlling changes to the project scope Goals of scope control are to: –Influence the factors that cause scope changes –Assure changes are processed according to procedures developed as part of integrated change control –Manage changes when they occur Variance is the difference between planned and actual performance. Control variances 3

Lesson 12: Monitoring and Controlling Project Schedule and Costs Topic 12A: Control the Project Schedule Topic 12B: Control Project Costs

5 Control Project Scheduling

6 A project is a collection of tasks that must be completed in minimum time or at minimal cost. Objectives of Project Scheduling –Completing the project as early as possible by determining the earliest start and finish of each activity. –Calculating the likelihood a project will be completed within a certain time period. –Finding the minimum cost schedule needed to complete the project by a certain date. 5.1 Introduction

7 A project is a collection of tasks that must be completed in minimum time or at minimal cost. Objectives of Project Scheduling –Investigating the results of possible delays in activity’s completion time. –Progress control. –Smoothing out resource allocation over the duration of the project. 5.1 Introduction

8 Tasks are called “activities.” – Estimated completion time (and sometimes costs) are associated with each activity. – Activity completion time is related to the amount of resources committed to it. – The degree of activity details depends on the application and the level of specificity of data. Task Designate

9 Identifying the Activities of a Project To determine optimal schedules we need to –Identify all the project’s activities. –Determine the precedence relations among activities. Based on this information we can develop managerial tools for project control.

10 Identifying Activities, Example XYZ. COMPUTERS, INC. XYZ. Computers manufactures personal computers. It is about to design, manufacture, and market the New Computer.

11 There are three major tasks to perform: – Manufacture the new computer. – Train staff and vendor representatives. – Advertise the new computer. XYZ. needs to develop a precedence relations chart. The chart gives a concise set of tasks and their immediate predecessors. XYZ. COMPUTERS, INC

12 ActivityDescription APrototype model design BPurchase of materials ManufacturingCManufacture of prototype model activitiesDRevision of design E Initial production run ActivityDescription APrototype model design BPurchase of materials ManufacturingCManufacture of prototype model activitiesDRevision of design E Initial production run FStaff training Training activitiesGStaff input on prototype models HSales training FStaff training Training activitiesGStaff input on prototype models HSales training Advertising activities IPre-production advertising campaign JPost-redesign advertising campaign Advertising activities IPre-production advertising campaign JPost-redesign advertising campaign XYZ. COMPUTERS, INC

13 From the activity description chart, we can determine immediate predecessors for each activity. Activity A is an immediate predecessor of activity B, because it must be competed just prior to the commencement of B. AB XYZ. COMPUTERS, INC

14 Precedence Relationships Chart XYZ. COMPUTERS, INC

15 The PERT/CPM Approach for Project Scheduling The PERT/CPM approach to project scheduling uses network presentation of the project to –Reflect activity precedence relations –Activity completion time PERT/CPM is used for scheduling activities such that the project’s completion time is minimized.

16 XYZ. COMPUTERS, INC. - Continued Management at XYZ. would like to schedule the activities so that the project is completed in minimal time. Management wishes to know: –The earliest and latest start times for each activity which will not alter the earliest completion time of the project. –The earliest finish times for each activity which will not alter this date. –Activities with rigid schedule and activities that have slack in their schedules.

17 Earliest Start Time / Earliest Finish Time Make a forward pass through the network as follows: –Evaluate all the activities which have no immediate predecessors. The earliest start for such an activity is zero ES = 0. The earliest finish is the activity duration EF = Activity duration. –Evaluate the ES of all the nodes for which EF of all the immediate predecessor has been determined. ES = Max EF of all its immediate predecessors. EF = ES + Activity duration. –Repeat this process until all nodes have been evaluated EF of the finish node is the earliest finish time of the project.

18 Earliest Start / Earliest Finish – Forward Pass A 90 B 15 C5C5 F 25 I 30 G 14 D 20 E 21 H 28 J 45 90,105 90,115 90, , , , , , , , , A 0,90 B I FCG D EH J EARLIEST FINISH

19 Latest start time / Latest finish time Make a backward pass through the network as follows: –Evaluate all the activities that immediately precede the finish node. The latest finish for such an activity is LF = minimal project completion time. The latest start for such an activity is LS = LF - activity duration. –Evaluate the LF of all the nodes for which LS of all the immediate successors has been determined. LF = Min LS of all its immediate successors. LS = LF - Activity duration. –Repeat this process backward until all nodes have been evaluated.

20 B F C A I E D G H H ,194 J J ,194 E ,194 90,105 90,115 90, , , , , , , , , ,149 0,90 129,149 D ,149 G ,129 I ,149 29,119 C5C5 110,115 B 15 95,110 5,95 F 25 90, 115 0,90 A 90 Latest Start / Latest Finish – Backward Pass

21 Activity start time and completion time may be delayed by planned reasons as well as by unforeseen reasons. Some of these delays may affect the overall completion date. To learn about the effects of these delays, we calculate the slack time, and form the critical path. Slack Times

22 –Slack time is the amount of time an activity can be delayed without delaying the project completion date, assuming no other delays are taking place in the project. Slack Time = LS - ES = LF - EF Slack Times

23 Critical activities must be rigidly scheduled Critical activities must be rigidly scheduled Slack time in the XYZ. Project

The critical path is a set of activities that have no slack, connecting the START node with the FINISH node. The critical activities (activities with 0 slack) form at least one critical path in the network. A critical path is the longest path in the network. The sum of the completion times for the activities on the critical path is the minimal completion time of the project. The Critical Path

25 B F C A I E D G H H ,194 J J ,194 E ,194 90,105 90,115 90, , ,129129, , , ,194 D 20 0,90 129,149 G ,129 I ,149 A 90 C5C5 110,115 B 15 95,110 F 25 90, 115 0,90 The Critical Path

26 We observe two different types of delays: –Single delays. –Multiple delays. Under certain conditions the overall project completion time will be delayed. The conditions that specify each case are presented next. Possible Delays

27 A delay of a certain amount in a critical activity, causes the entire project to be delayed by the same amount. A delay of a certain amount in a non-critical activity will delay the project by the amount the delay exceeds the slack time. When the delay is less than the slack, the entire project is not delayed. Single delays

28 LS =119 A 90 J 45 H 28 E 21 D 20 I 30 G 14 F 25 C5C5 B 15 ES=149 LS=173 DELAYED START=149+15=164 ES=90 DELAYED START=90+15 =105 Activity E and I are each delayed 15 days. THE PROJECT COMPLETION TIME IS NOT DELAYED FINISH Multiple delays of non critical activities: Case 1: Activities on different paths

29 A90 90 B15 Gantt chart demonstration of the (no) effects on the project completion time when delaying activity “I” and “E” by 15 days. Activity I F25I C5 115 G D E 21 H28 J Activity E

30 A 90 B 15 C 5 F 25 I 30 G 14 D 20 E 21 H 28 J 45 FINISH ES=149 LS =173 DELAYED START= =164 ES=90 DELAYED START =94 LS =95 THE PROJECT COMPLETION TIME IS NOT DELAYED Multiple delays of non critical activities: Case 2: Activities are on the same path, separated by critical activities. Activity B is delayed 4 days, activity E is delayed 15 days

31 A 90 B 15 C 5 F 25 I 30 G 14 D 20 E 21 H 28 J 45 FINISH DELAYED START= =113; ES= 90 DELAYED START =94 DELAYED FINISH = 94+15=109 LS =110 3 DAYS DELAY IN THE ENTIRE PROJECT Activity B is delayed 4 days; Activity C is delayed 4 days. THE PROJECT COMPLETION TIME IS DELAYED 3 DAYS Multiple delays of non critical activities: Case 2: Activities are on the same path, no critical activities separating them.

32 A Linear Programming Approach to PERT/CPM Variables –X i = The start time of the activities for i=A, B, C, …,J –X(FIN) = Finish time of the project Objective function –Complete the project in minimum time. Constraints –For each arc a constraint states that the start time of M must not occur before the finish time of its immediate predecessor, L. ML

33 A Linear Programming Approach Define X(FIN) to be the finish time of the project. The objective then is Minimize X(FIN) While this objective function is intuitive other objective functions provide more information, and are presented later.

34 X(FIN) ³ X E + 21 X(FIN) ³ X H + 28 X(FIN) ³ X J + 45 X D ³ X G + 14 X E ³ X D + 20 X G ³ X C + 5 X H ³ X D + 20 X G ³ X F + 25 X J ³ X D + 20 X I ³ X D + 90 X J ³ X I + 30 X F ³ X A + 90 X C ³ X B + 15 X D ³ X G + 14 X B ³ X A + 90 G C5C5 F 25 All X s are nonnegative Minimize X(FIN) ST A Linear Programming Approach

35 Minimize X A +X B +…+X J This objective function ensures that the optimal X values are the earliest start times of all the activities. The project completion time is minimized. Maximize X A +X B +…+X J S.T. X(FIN) = 194 and all the other constraints as before. This objective function and the additional constraint ensure that the optimal X values are the latest start times of all the activities. A Linear Programming Approach

36 Obtaining Results Using Excel

37 Gantt Charts Gantt charts are used as a tool to monitor and control the project progress. A Gantt Chart is a graphical presentation that displays activities as follows: –Time is measured on the horizontal axis. A horizontal bar is drawn proportionately to an activity’ s expected completion time. –Each activity is listed on the vertical axis. In an earliest time Gantt chart each bar begins and ends at the earliest start  finish the activity can take place.

38 Here‘s how we build an Earliest Time Gantt Chart

39 A90 90 B15 F25 I C5 115 G D E21 H28 J45 194

40 Gantt chart can be used as a visual aid for tracking the progress of project activities. Appropriate percentage of a bar is shaded to document the completed work. The manager can easily see if the project is progressing on schedule (with respect to the earliest possible completion times). Gantt Charts- Monitoring Project Progress

41 A 90 B 15 F 25 I 30 C 5 G 14 D 20 E 21 H 28 J Monitoring Project Progress The shaded bars represent completed work BY DAY 135. Do not conclude that the project is behind schedule. Activity “I” has a slack and therefore can be delayed!!!

42 Advantages. –Easy to construct –Gives earliest completion date. –Provides a schedule of earliest possible start and finish times of activities. Disadvantages –Gives only one possible schedule (earliest). –Does not show whether the project is behind schedule. –Does not demonstrate the effects of delays in any one activity on the start of another activity, thus on the project completion time. Gantt Charts – Advantages and Disadvantages

43 Resource Leveling and Resource Allocation It is desired that resources are evenly spread out throughout the life of the project. Resource leveling methods (usually heuristics) are designed to: –Control resource requirements –Generate relatively similar usage of resources over time.

44 A heuristic approach to “level” expenditures –Assumptions Once an activity has started it is worked on continuously until it is completed. Costs can be allocated equally throughout an activity duration. Step 1: Consider the schedule that begins each activity at its ES. Step 2: Determine which activity has slack at periods of peak spending. Step 3: Attempt to reschedule the non-critical activities performed during these peak periods to periods of less spending, but within the time period between their ES and LF. Resource Leveling – A Heuristic

45 Management wishes to schedule the project such that – Completion time is 194 days. – Daily expenditures are kept as constant as possible. To perform this analysis cost estimates for each activity will be needed. Resource Leveling – XYZ. COMPUTERS. - continued

46 Resource Leveling – XYZ. COMPUTERS,– cost estimates

47 Cumulative Daily Expenditure – Earliest Times vs. Latest Times Level Budget Earliest Start-Earliest Finish Budget Latest Start-Latest Finish Budget Feasible Budgets Time

EHJEHJ J Cost Leveling EJEJ EJEJ HJHJ H CFCF A BFBF I I H Daily Expenditure of the ES Schedule 55 IIIII 25 I I I ES = 90 I LS = I I IFIF G D

49 G EHJEHJ J I EJEJ EJEJ HJHJ CFCF A BFBF I I H H H Cost Leveling I D IFIF

50 The Probability Approach to Project Scheduling Activity completion times are seldom known with 100% accuracy. PERT is a technique that treats activity completion times as random variables. Completion time estimates are obtained by the Three Time Estimate approach

51 The Three Time Estimate approach provides completion time estimate for each activity. We use the notation: a = an optimistic time to perform the activity. m = the most likely time to perform the activity. b = a pessimistic time to perform the activity. The Probability Approach – Three Time Estimates

52 Approximations for the mean and the standard deviation of activity completion time are based on the Beta distribution. The Distribution, Mean, and Standard Deviation of an Activity

53 To calculate the mean and standard deviation of the project completion time we make some simplifying assumptions. The Project Completion Time Distribution - Assumptions

54 Assumption 2 –The time to complete one activity is independent of the time to complete any other activity. Assumption 3 –There are enough activities on the critical path so that the distribution of the overall project completion time can be approximated by the normal distribution. The Project Completion Time Distribution - Assumptions Assumption 1 –A critical path can be determined by using the mean completion times for the activities. –The project mean completion time is determined solely by the completion time of the activities on the critical path.

55 Mean = Sum of mean completion times along the critical path. The three assumptions imply that the overall project completion time is normally distributed, the following parameters: The Project Completion Time Distribution Variance = Sum of completion time variances along the critical path. Standard deviation =  Variance

56 The Probability Approach – XYZ. COMPUTERS

57 Management at XYZ. is interested in information regarding the completion time of the project. The probabilistic nature of the completion time must be considered. The Probability Approach – XYZ. COMPUTERS

58  A = [76+4(86)+120] / 6 = 90   = ( ) / 6 = 7.33  A 2 = (7.33) 2 =  XYZ. COMPUTERS – Finding activities’ mean and variance

59 The mean times are the same as in the CPM problem, previously solved for XYZ. Thus, the critical path is A - F- G - D – J. –Expected completion time = m A +m F +m G +m D +m J =194. –The project variance =s A 2 +s F 2 +s G 2 +s D 2 +s J 2 = –The standard deviation = =  XYZ. COMPUTERS – Finding mean and variance for the critical path

60 The probability of completion in 194 days = The Probability Approach – Probabilistic analysis 194

61 An interval in which we are reasonably sure the completion date lies is  z The Probability Approach – Probabilistic analysis.95  The interval is = 194 ± [175, 213] days. The probability that the completion time lies in the interval [175,213] is 0.95.

62 XZXZ The probability of completion in 180 days = P(X  180) = P(Z  -1.51) = = The Probability Approach – Probabilistic analysis

63 The probability that the completion time is longer than 210 days = XZXZ ? The Probability Approach – Probabilistic analysis

64 The Probability Approach – Critical path spreadsheet

65 The Probability Approach – critical path spreadsheet A comment – multiple critical paths In the case of multiple critical paths (a not unusual situation), determine the probabilities for each critical path separately using its standard deviation. However, the probabilities of interest (for example, P(X ³ x)) cannot be determined by each path alone. To find these probabilities, check whether the paths are independent. If the paths are independent (no common activities among the paths), multiply the probabilities of all the paths: [Pr(Completion time³x) = Pr(Path 1³x)P(Path 2³x)…Path k³x)] If the paths are dependent, the calculations might become very cumbersome, in which case running a computer simulation seems to be more practical.